Responding to a question by a BBC reporter about whether he saw Navalny as a political competitor, President Putin said , "When I heard you were from the BBC, I didn't doubt for a moment you would ask precisely that question because it's in a certain sense propaganda of the people whom you support".

The Russian president, who was speaking during his annual televised phone-in, ignored more biting questions from viewers about Alexei Navalny and his plans to stand for a fourth term.

The remarks appeared on-screen in an apparent glitch, AFP reported.

Navalny's video accusing Prime Minister Dmitry Medvedev of massive corruption has been viewed 23 million times on YouTube.

"Any form of protest, including demonstrations, should remain in the framework of the law," Putin said. "Those who violate the law must answer for these violations."

Navalny has been sentenced to 30 days behind bars after being detained Monday on his way to a protest in Moscow against government corruption. He has announced his intention to stand for president against Putin in 2018

"Is true that Navalny is making a film about you now?" a viewer asked.

"Putin, do you really think people believe this circus with staged questions?" asked another.

Several called for an end to Putin's rule, ahead of elections next year when he is widely expected to stand for a fourth term.

The Russian president also said the latest US sanctions over alleged election meddling were efforts to "contain Russia".

On Wednesday, the US Senate voted overwhelmingly to approve further sanctions against Russia.

Comparing James Comey with fugitive whistleblower Edward Snowden, Putin jokingly suggested he could offer political asylum to the sacked FBI director.

"If he is persecuted, we would be ready to offer him asylum in Russia. He should know this," Putin said.

Comey, who was overseeing the probe of Russia's involvement in the US elections, was recently sacked by US President Trump.

Snowden, a former contractor for the CIA, was given asylum by Russia for leaking classified information from the National Security Agency to journalists.

Vladimir Putin, who is usually closely-guarded about his personal life, told Russian media for the first time that he has grandchildren. He said he wants to keep them out of the spotlight so they can grow up "normally".

On the phone-in show, Putin said that one grandson was born recently, to applause in the studio, while another is "already in preschool".

"The thing is, I don't want them to grow up like hereditary princes, I want them to grow up to be normal people," Putin said in explaining the secrecy around his family.

"If I mention ages and names, they would be identified and never left alone."